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New Scientist Live

Bioluminescent bloom makes beach a magical minefield

See more:To see the image this article refers to, keep checking Picture of the Day on our news blog Short Sharp Science

By Rowan Hooper

IT DOESN’T get much better than this. It’s a moonless night and you are on a deserted beach in the Maldives. As the waves lap the shore, the beach lights up like Las Vegas. Glowing organisms stick to your feet. It is one of the most magical sights in the natural world&colon; a bloom of bioluminescent plankton.

This picture was taken on Vaadhoo Island, but bioluminescing organisms are found all over the world. The ones here are probably single-celled protists and marine crustaceans called copepods. Both glow when they are disturbed.

“Every so often, one of these bright specks of light would appear to take off and run up the beach,” says photographer Doug Perrine. Ghost crabs were grabbing the glowing organisms and carrying them back to their burrows.

It doesn’t work so well on the beach, but bioluminescence usually distracts predators by disrupting their swimming behaviour and preventing them from feeding. It may also act as a burglar alarm to attract animals that feed on the predators. So what to us is a beautiful spectacle of light is to them a minefield (Journal of Plankton Research, DOI&colon; 10.1093/plankt/fbh141).

The light is produced by devilishly named twins&colon; a pigment called luciferin and an enzyme, luciferase. Luciferin reacts with oxygen, and luciferase speeds up the reaction. A range of unrelated animals use the same pigment-enzyme pair to produce light, including fireflies, anglerfish and jellyfish. Bioluminescence evolved independently many times&colon; in the bigger picture, it ain’t so magical after all.